Edge of Seventeen
by flannelcastiel
Summary: Dean and Castiel are friends-which is complicated by Castiel's ever-evident feelings for the Alpha in his English class. And then everything goes awry when his heat suppressants stop working. Alpha/Beta/Omega dynamics. Omega!Castiel. Alpha!Dean. A/B/O. Knotting. Explicit. I may add more to this verse later on, but complete for now.
1. Chapter 1

_**Rating:**__ R_

_**Summary:**__ Dean and Castiel are friends-which is complicated by Castiel's ever-evident feelings for the Alpha in his English class. And then everything goes awry when his heat suppressants stop working._

_**A/N:**__ My first stab at the a/b/o!verse. Unbeta'd too._

* * *

For the first time in his short life, Castiel is truly afraid.

Before the fear, though, came a unique pulse of joy. When the second semester of his Junior year at university began, Castiel met Dean. Dean's a Mechanical Engineering major, and Castiel is double majoring in Dynamic Studies and Psychology. They meet in the middle, stuck in the same English prerequisite class-and they are assigned to sit next to one another. Dean was honestly very attractive, but Castiel was uninterested. He has never been interested in anyone, especially not an Alpha.

He tries not to be one of those resentful Omegas who reverses the prejudice. He does not want to bear a cross for his people, and the way they suffered in generations past. Instead he embraces the new equality that comes with the enlightened age, where Alphas, Betas, and Omegas all can pluck ripened fruit from the same tree-have the same jobs with the same pay, eat at the same public establishments, and so forth. And most importantly, Omegas are no longer subjected to cruel sexual objectification. Generally.

Castiel still does not think that he will ever mate, because there is a stain of prejudice on his heart. He does not show it in the form of hateful speech or protest, or even subtle disrespect. He inflicts the righteous anger upon himself, by swearing that he shall never mate or tie or surrender to any primitive instinct. He started taking suppressants as soon as he started puberty, and he had only been in heat once... he was miserable, but he overcame the wave of needneedknotneed with an impressive amount of resilience.

So naturally, Dean Winchester could not possibly faze his resolve. At first.

Castiel becomes afraid when he hears Dean's voice and his whole body jerks to attention. When Dean laughs, Castiel cannot help but smile with him. Eventually, Castiel begins to stare too long, eyes watchfully glued to Dean's hand as he writes in his sloppy script. Dean has nice hands, and he really knows his resolve is rupturing when he absently wonders how soft they are, how they would feel running down the cleft of his ass-

He does not want to want. Castiel has lived nearly twenty-two years without giving in to the social norms, because his pride and his beliefs far outweighed any pleasure objectification and humiliation might bring him. Not that all Alphas treated their mates like...like pets, but just as Castiel knows that submission is in his blood, he knows that domination is in Alphas'.

And of course as soon as his internal turmoil begins, Dean turns his head slightly to look at Castiel, and of course he's caught staring. His pulse thrums in his neck and in his hands as he clenches his fists. The professor speaking is just ambient noise now. Dean's innocent glance in Castiel's direction morphs into one of shock, and then invested concentration. His heart continues to hammer incessantly and he has to dig his nails painfully into his palms to snap this trance. Castiel unceremoniously drops his eyes to his notebook and continues to jot down mindless notes that may or may not have anything to do with the English language.

Castiel is good at hiding. In high school, he lived and breathed to be less noticeable. The region where he grew up still was accustomed to old tradition, in which Omegas were subservient to Alphas and Betas. It is only because his elder brother, Michael, was an Alpha that Castiel never received a thorough beating or was harassed. Everyone feared Michael, and therefore let Castiel be. Still, he was a target for much ridicule.

He hopes that Dean will not think that Castiel is skipping English lectures on his part. Even though that is most certainly the case, Castiel does not want Dean to suspect his...his fascination more than he must already.

The night grows restless, Castiel tossing and turning like his mattress is made out of stone. He's sore up his sides, and his blood feels too hot not to be boiling. For a few hours, he considers that this is just a sudden onset of the flu, caused by stress. But as the sun sets and Castiel's fingers are twisting in the sheets, his hips gyrating in the air with no clear purpose, he realizes what is happening.

He throws himself from the bed, and scrambles to the bathroom. He's grateful he has a private dorm with its own attached bathroom, where he can be in privacy as he pulls down his underwear slightly in front of the mirror. His penis is swollen, aching, and leaking pre-come down the short shaft. Castiel tucks it away without touching it, hoping that if he ignores it this will stop. The next thing he does is check his medicine cabinet and pulls out his suppressants. Each day's pill is individually packaged, and he can see the empty space where today's pill should be. In the near ten years he's been on the pill, it's never failed him and now...

Castiel slams a hand into the wall, frustration and anger curling on a whimper that escapes his throat. It happens eventually, they say. It's biologically unhealthy to go so long without a cycle, they say. But why now, when he's suddenly very much attracted to his closest friend and classmate-he wants to be free of this weight, because he does not trust himself. He does not trust anyone.

A loud knock on his dorm's door startles Castiel, and he scrambles to splash some cold water on his face before going to answer. Pulling his jacket a little tighter across his chest, he steps lightly to the door, and cracks it.

"Cas?"

It's Dean-shit, it's Dean.

Castiel shudders and keeps the door barely cracked, licking his lips and most definitely staring at Dean's shoes and not his eyes-though he can see them still: wide and green and concerned, as Dean always is and always will be because that's just him. Infinitely compassionate and caring and...Castiel does not think he's perfect-no one is perfect.

"Cas are you okay?" He sounds so concerned, and Castiel sees his fingers inching into the door frame, and he's trying to get inside.

Castiel feigns a cough. "Flu," he groans miserably, making sure to mask the fleeting moan buried in the pit of his stomach that threatens to escape.

"You're lying," Dean says, and he's subtly trying to get through the door.

For a fleeting moment, Castiel is reminded that Dean is an Alpha, and Castiel is in heat. His core belief system is ignited, and his mouth sets hard. "Go away, Dean," he bites out.

Dean's brows raise, and it almost seems like he flinches from Castiel's words. "I was just tryin' to make sure you're alright..."

"And I am," Castiel snaps. "Your curiosity is satiated, so do not-don't-just leave."

"What the hell is wrong with you?" Dean asks firmly, but quiet. He doesn't want to appear threatening, Castiel notes, idly curious beneath his annoyance.

"You know," Castiel murmurs. All the Alphas in his dorm can probably smell a hint of his scent now, circulating in the vents. All the more reason to hide in his shower stall until it blows over.

Dean stiffens. "Now I know-yeah, but I'm not going to do anything about it." Castiel's shoulders visibly loosen at his remark, though he's still doubtful, and Dean's eyes go wide. "You think-you think I'm that weak? Cas I would never do that!"

It's Castiel's turn to look shocked, even hurt. It did not even occur to him that Dean would be offended by Castiel's perception of his self-control. "I thought..."

"You thought wrong. Damn it, Cas, just let me in."

He lets Dean in, wrapping his arms around his abdomen and falling into his bed. He whimpers slightly at the pressure between his legs and adjusts until most of his weight is on his hip, not his backside. Dean pulls up the desk chair next to him.

"Just 'cause I'm an Alpha doesn't mean I'm gonna fuck my friend, okay," Dean whispers. "I-I've got a lot of respect for Betas and Omegas, and... I know how to control it. I'm good at it."

"Does...does my scent bother you?"

"No," Dean replies quickly, and it's not completely truthful as far as Castiel can tell. "It's nice...really nice. I really thought you were pissed at me, but then you opened your door and...wow. But I'm fine with it, really. You're my best friend, Cas, and I'm not gonna let some animal instinct change that."

There is a warmth bubbling in his stomach, as he raises his eyes to Dean's. They're so warm, even though there is no challenge that Dean's eyes are the coolest and brightest that he's ever seen. They flick in the lamp light with flakes of gold and silver, and Castiel is sure he's imagining how lovingly Dean stares at him.

He turns his head into the pillow and huffs a frustrated breath, hoping he can will these feelings away. The heat is only growing stronger, but he realizes that it's not just in his body, but set in his thoughts and growing with each thrust of his heart against his ribcage.

Dean touches his hand, and it's cold. He squeezes it, hoping the touch will cool the rest of him, but it only makes Castiel grow hotter.

"I apologize for misjudging you, Dean," Castiel murmurs, turning his head once more so that he's looking at Dean. "I... I have many preconceived notions about Alphas, most of which you have challenged."

"Huh," Dean says. "Like being a dumb, sex-craving animal who wants to throw every Omega in heat into the bed and fuck them whether he or she gives me the go or not?"

Castiel blushes. "Roughly. I'm sorry."

"No, I get it," he replies. "But why me? I'm not the only nice Alpha in town."

"You are many things, and nice is the least accurate description."

"Hey!" Dean objects.

"No...I'm trying to compliment you." It's a quiet confession, prologued by a deep breath. "You are beautiful, Dean. Inside, outside. I...have feelings for you." His heart rate increases even more, if that's possible, and he dares not look into Dean's eyes.

There is silence for a long moment, then Dean decidedly speaks. "Is this the heat talking?"

Castiel hasn't even stopped to ponder this until Dean airs the concern. He thinks-he was not experiencing any symptoms of going into heat in his last English lecture. If anything, Dean triggered this tidal wave of need-is that even possible? Could pure, unadulterated attraction overwhelm his own body's chemistry and negate his suppressants?

It does not matter at this point, Castiel decides. "No. Before." He squeezes Dean's hand back. "I look at you...and I see." It makes no sense, he thinks, except to him. Hearing Dean's opinions about equality and love and acceptance, recognizing that he's sweet and intelligent and not a simple mindless tramp in search of a good fuck, it gives Castiel a new lens to peer through. A lens of hope.

"Me too," Dean whispers back, and he's getting closer. He sniffs and can even smell Dean now, want wafting off him in voluptuous waves. Castiel feels a sense of completeness, because Dean gets it. Dean sees.

And this is the moment where Castiel falls in love with Dean Winchester, his best friend-an Alpha. And it's also the moment he accepts that... he wants. And finally, the idea of surrendering to that most primitive instinct does not incite fear in Castiel's body. For once, he's not afraid. He's ready.


	2. Chapter 2

Though he's ready, reservations still lay awake beneath his skin. He presses back into his bed, scooting away from Dean. But Dean still holds his hand tighter than ever, his mouth turning into a wayward grimace. Castiel tries not to look at him, but his eyes are drawn like magnets to Dean.

His thoughts whisper an always, a reminder that these emotions-this need-lay dormant in his skin prior to being overwhelmed by his cycle, even in its early stages. The reminder of the chemistry occurring in his body makes Castiel's nose twitch-and-and he can smell it. Dean. It's not something very meaningful, because Dean looks concerned. But on a biological level Dean's responding to Castiel, to Castiel's scent. With all Dean's self-control, Castiel knows that...copulation is inevitable. Regardless if either want each other in that way, they will need it.

Castiel does need it-it being something to fill his aching hole. It's already dilating, pheromones spilling from each and every pore to beckon the first willing Alpha. But does he want it? Something tells Castiel that he does, based on the fluttering in his stomach and his fixation with Dean's gaze, but he has no idea if Dean feels the same. The trouble with an Alpha and Omega being together is the baggage that comes with their chemistry. What is want? What is need? What is...love?

He wills himself not to get caught up in the philosophical nature of this moment and just...live. He licks his lips and squeezes Dean's hand tighter. "Do you want me, Dean?" he asks, and it's barely a whisper. He has to take a deep breath when he sees Dean nod just a little, and with it he inhales the rough and musky scent rolling of Dean in waves. "Dean, how long?"

Without a word, Dean pulls Castiel's hand to his lips. He shivers when Dean presses soft kisses to each knuckle, letting his eyes close as he grazes Castiel's fingers up and down his stubbled cheeks. "Since day one."

Castiel is whimpering as Dean presses kisses down his wrist, his forearm. Dean is kissing him, he realizes with a gasp of shock. Dean, his friend, is suddenly Dean his...his lover. Soon-to-be lover. Both-Castiel doesn't care and cannot find himself to label anything or raise any concern when those luscious and irresistibly full lips are covering his skin like it's some sort of sweet.

He weaves his fingers into Dean's short sand-colored hair and maneuvers those lips higher-Castiel is too impatient to wait for Dean's ascension-and their lips collide. Dean tastes even better than he smells, and Castiel feels himself opening wider, anticipating penetration. He's making little noises into Dean's mouth, lifting his hips into the air. In a moment, Dean is rolling from his chair onto the bed, on top of Castiel. His eyes are hooded as he stares down at Dean, his necklace dangling and brushing against Castiel's lips. He cannot resist taking the bronze piece between his teeth and biting. Small barely perceivable indentations are made, and Dean pants a hot breath into Castiel's face before taking his mouth again.

"Dean..." Castiel croaks. "Dean, please, I can't-I can't wait. Please."

Dean smiles and kisses the side of Castiel's mouth, swallowing the string of hapless whining that follows his plea. "Shhh, I need to do this right."

"Do it right later," Castiel urges, lifting his hips to Dean's.

It's a quick shock when Dean's palms grab Castiel's hips roughly and pushes them back into the mattress. He cries out, his backside twitching from the slightest pressure. Dean looks hot, mouth set and face red as he separates their hips. "No," he states firmly, dropping his mouth to Castiel's ear. "My way."

Castiel shivers, not anticipating that his body temperature would surely double at the thought of being controlled-at Dean controlling him. This is the root of Omega prejudice-domination and submission. Except he doesn't care-because he wants to submit to Dean.

And only Dean.

He closes his eyes and mouths an apology, because his vocal chords are useless at this point, and shudders as Dean's mouth attaches to the base of his neck. Dean suckles and brushes his teeth, making a bruise that will probably be there for days to come. He presses his sweaty palms into the back of Dean's neck, sucking in a breath when Dean moans into his skin. He strokes Dean's neck, rolling the pads of his fingers against the tense ring of muscles.

"Cas..." he sighs, and Castiel cannot bear this. He cannot bear being sucked and kissed and left out dry and needy.

"I need you, Dean," he manages in one growling breath. Dean lifts his face to see Castiel's eyes and nods firmly.

Both of their clothes come off in hasty, desperate movements. Before long, Castiel is sweaty and naked bellow Dean, is little cock erect and flopping against his stomach as he gyrates his hips against the bed. Dean rests his knees on Castiel's spread thighs, effectively holding him down while he took in Castiel's visage. He runs his hands up Castiel's legs, his sides-skims his fingernails over Castiel's nipples until he's shuddering from the sensation.

"You're so pretty for me," he murmurs absently. He leans down, kisses Castiel's stomach and then takes on nipple into his mouth. He sucks at it generously, and Castiel feels the blood rushing to it, hardening it, and his breasts swelling. He-he never sexualized his nipples before. He knew it was where pups would seek their milk, even if he never planned on having pups. Though, his entire paradigm has likely shifted by now. Everything is different with Dean. He wants new things. He needs.

Dean pops of Castiel's nipple, and smiles when he moans. They resume passionately kissing, but Dean is suddenly wrapping his hands around Castiel's lower back and shifting his fingers down his ass and-and-

"Yes!" Castiel cries against Dean's lips and thrusts upward, allowing Dean's fingers an easier entrance into his dilated hole. He's still tight, when Dean inserts two fingers and presses at the ring of muscles. Castiel, in this state, cannot even moan properly without his breath hitching, his lips begging for Dean's like a man in a desert searching for water. He's yearning for more, he's sure, but Dean is taking his time in stretching his soaking hole.

"Talk to me," Dean murmurs against his lips. "I wanna hear you beg for my knot."

"I-I-" Castiel tries, but every attempt to form a coherent thought is lost when Dean's fingers dig a little deeper and find-they find it-the bundle of sensitive nerves that send crackling lightning through his bones and make his vision white. He's sure he is done for-satiated-but Dean takes his fingers away before he can succumb.

"Don't you wanna wait for me?" Dean whispers huskily, licking his lips. "I need you to talk to me, Cas." How is he he so constructed? Castiel can feel his throbbing heat rutting against his thigh, the musk tumbling off his skin, which effectively paralyzes Castiel into a comatose state of pleasure. Yet he taunts, he plays with Castiel's body like it's an instrument in need of tuning.

"I do," Castiel breathes after a long moment of absence and emptiness. His hole contracts, wanting to latch around something full and hard and wet. "I do want...I want to cum on you, all over your knot..."

"Yeah," Dean pants and kisses him full on the lips, He spreads Cas' legs a little wider, and his fingers approach from this new angle as he sits back. "So open for me. How long have you wanted this?"

"Never," Castiel answers quickly and honestly. "I have never...my surpressents..." His explanation is lost even to him, but Dean quickly becomes privy to the words' context.

"You-you're a-Cas, are you a virgin?" Dean murmurs. Castiel should be embarrassed, but he's too fucking hot and needy to do anything but nod furiously.

"Yes and I need that to change," he mumbles incoherently. "Need...need you...please."

Dean scissors his fingers in Castiel's hole, satiating his plea, and once he's stretched and fully dilated Dean's cock presses against the entrance and-

Yes, his entire being hisses as he arches his back, twists his fingers into the messy bedding all around him. Dean sheathes himself quickly in one quick slide, only taking two thrusts to make him fully erect and locked inside Castiel's little cunt. Their bodies rut and rub as Dean hammers inside him, almost always hitting the sweet spot of nerves and making Castiel actually scream. Dean holds his face, kisses it some, but mostly just stares whether Castiel can keep his eyes open or not. Praise fills the air with each and every thrust, and Castiel cannot even believe he's conscious.

"Cas your so beautiful, you've always been-you're perfect. Too good for me...too good, Cas...perfect..."

Between the praise and the kisses and touching and the all-but-tentative fucking, a white hot fire bubbles in Castiel's core. He digs his blunt nails into Dean's shoulders, pulling him close so that he can wind his arms around Dean's neck. Their next kiss is long, languid, and full of the words he can't form vocally. Dean's grunting and thrusts become more erratic, and Castiel feels a boundless spring loading deep within him as Dean hits the most precious and sensitive spot inside him over and over. They clutch each other, recklessly abandoning any notion of keeping this going. It must end, and it has to, it has to because Dean's swelling more and more, cuming before his climax is even reached, soaking Castiel's hole and making a wet hot mess before it's all over.

"I'm close," Dean tells Castiel in a furious whisper. Castiel answers with a prolonged whimper. "Cas, please, come for me...right now... Cas!" He grunts and he's pulsing each and every drop of his fluid into Castiel, and Castiel comes soon after from the sensation. Their hips rut against each other as Castiel's contracting muscles pull and milk Dean of every last drop. Soon, both of them have softened and Dean pulls out slowly with a shuddering sigh, and then collapses beside Castiel

Castiel pulls his limp body into the crook of Dean's sweaty arm and awaits the acceptance, the loving touch of Dean wrapping around him. When he does, he is content. Quickly, he falls to rest, enraptured by warmth and a happiness he has yet to find elsewhere in such copious amounts.

"Cas, let me walk you home," Dean tells him several weeks later after class. The first night they had together-and the last, thus far-was one filled with confessions worthy of other ceremonious declarations. It was after Castiel awoke to a hot breakfast in his lap and a beautiful and loving Dean laying next to him that he realized how hopeless lost he was. And being lost wasn't a bad thing, he realized, when Dean had him. He felt safe. He was in love.

And Dean said as much, that morning, which disappointed Castiel because he wanted to say it first. But he does return the words. They kissed sweetly before Dean watched happily as Castiel devoured his scrambled eggs and blueberry muffin.

Only a week later did they agree to move in together, since they shared beds most nights anyhow. They touched, they slept. Nothing more.

So when Dean offers to walk Castiel home, it's odd, because they have the same home now. Except Dean has one more class today, a night class, and Castiel will be walking home tonight otherwise. Still he asks the question. "Why? Am I not capable of finding my way home without you?"

"No," Dean mutters, not appreciating Castiel's tone, clearly. "It's just-you-" He stops and takes a ragged breath. "Your scent. You're going into heat."

Castiel stops walking. "I-not again!" is his only response. Once again, his surpressents have been rendered useless. He will have to consult his doctor about changing brands or something. The only factor in his life that's changed is Dean Winchester. Dean Winchester is not optional, but he cannot spend the rest of his days out of control of his cycles.

"Hey," Dean murmurs, touching his arm. Castiel relaxes at the touch and lets it become just a little more. Their fingers weave together, and Dean does that thing-the thing where he brings Castiel's fingers to his mouth and kisses them so tenderly. "Have you thought about...just letting your cycles set in?"

"No," Castiel answers quickly, honestly, because he hasn't. Before it was completely necessary to keep himself irregular as possible. As in, once in nine years kind of irregular. But that was before he had any outlook of partnership, of an active sexual relationship. He hadn't even stopped to consider if Dean wanted more from him, and he frowns. "Do you want me to?" he asks sourly.

Dean reads the lines on his face, the downturn of his mouth and grimaces right back. "I'm not with you for the sex," he mutters indignantly. "I love you. I don't love your body, but it's a bonus. But I don't need the-the sex if you don't wanna..."

"It's not that I don't want to," Castiel replies shyly. "I don't like being in heat... feeling out of control of my own body."

"You don't have to be in heat, you know." Dean smirks. "Nothing says you gotta be like that to mess around. We could figure out what you like, what you don't like-all that stuff, when you're in control." He bends down to kiss Castiel's forehead. "And then I'll know what not to do, if that time of the month comes and-you need to get off."

"I...I never thought about it that way," Castiel admits. "Perhaps I'm more traditional than I thought...thinking that sex is to just ease the heat..."

"It really isn't. I'm perpetually horny," Dean sighs. "So any day of the week, just say the word, and I'm down with a little..." He smiles and wiggles his eyebrows. "Experimentation."

Castiel smacks him lightly on the shoulder, but his smile is fond. "I love you."

"Mhm," Dean murmurs doubtfully. "Sure you do."

"I...I do. Very much so." Castiel pauses and turns his eyes up the sky. "It's getting dark. I should get home."

"I am walking you," Dean reminds him as Castiel takes turns and begins to walk toward their dormitory.

"Yes, yes, I know." Castiel is grinning when he hooks his arm into Dean's, pressing his cheek into his firm shoulder. "I'm afraid that I'm going to have to ask you to skip your evening lecture, though. Nip this in the bud."

"Yeah?" Dean mutters softly beside him. Shy, how adorable.

"Yes. And if you're lucky...we'll be skipping all of our classes tomorrow."

How ironic, Castiel speaking of Dean's luck when he is most certainly the lucky one in this dynamic. How ironic indeed.


End file.
